Heavy metals such as mercury can be present in trace amounts in all types of hydrocarbon streams such as crude oils. The amount can range from below the analytical detection limit to several thousand ppbw (parts per billion by weight) depending on the source. It is desirable to remove the trace amounts of these metals from crude oils.
Various methods to remove trace metal contaminants in liquid hydrocarbon feed such as mercury have been disclosed.
U.S. Pat. Nos. 6,537,443 and 6,685,824 disclose processes for removing mercury, in which the liquid hydrocarbon feed is mixed with sulfur containing compounds, and removing the mercury-containing particulates in a pre-coated pressure filter. A filtering process is compact, but it may result in loss of hydrocarbons and waste in the form of oily solids. In US Patent Publication Nos. US20120067785A1, US20120067784A1, US20120125816A1, reactive extraction methods are employed, wherein the liquid hydrocarbon feed stream is brought into contact with additives including but not limited to an iodine source, tetrakis(hydroxymethyl)phosphonium sulfate/tetrakis(hydroxymethyl) phosphonium chloride, and oxidizing agents, respectively, wherein mercury is extracted from the crude oil into a water phase for subsequent removal.
There is a need for improved methods and systems for the removal of mercury from liquid hydrocarbon steams, particularly a compact system maximizing oil recovery and using lower quantities of chemical reagents than in prior art methods.